X-ray inspection device and X-ray inspection method

Abstract

To enable a seal inspection without reducing inspection accuracy of a content even if the content is thick.SOLUTION: An X-ray inspection apparatus 1 comprises: a packaging material detection sensor 4 which emits the X-ray while conveying an inspection object W in which a content Wb is wrapped by a packaging material Wa, inspects the quality of the inspection object W by using an X-ray image obtained by detecting the X-ray transmitting through the inspection object W, the inspection object W having a seal part Wc in which the packaging material Wa is sealed on one side of the content Wb, and which detects a specific position of the seal part Wc; content region extraction means 22 which extracts a content region of the inspection object W from the X-ray image; pseudo seal width calculation means 23 which calculates a distance to the outer edge on the one side of the content region from the specific position as the pseudo seal width H; and seal part determination means 24b which determines the seal failure when the pseudo seal width H is outside a prescribed range.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an X-ray inspection apparatus and an X-ray inspection method that inspect the quality of an object by irradiating the object with X-rays while transporting the object and detecting the X-rays that have passed through the object to obtain an X-ray image. [Background technology]

[0002] For example, in the case of a product in which the contents are placed through an opening in the packaging, the opening is sealed after the contents are placed in the packaging. At this time, the contents or foreign matter may get caught in the sealed area of ​​the packaging, causing a seal failure, and the product with this seal failure must be rejected as a defective product.

[0003] An example of an inspection device that inspects this type of product for defective sealing is the X-ray inspection device disclosed in Patent Document 1. The X-ray inspection device disclosed in Patent Document 1 uses an outline area extracted from an X-ray transmission image as a reference, calculates the sealed area based on preset seal information, and determines whether or not there is a defective seal using the shading level of the image within the sealed area. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-024549 Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, when inspecting whether contents or foreign objects are caught in the sealed area using the X-ray inspection device disclosed in the above-mentioned Patent Document 1, it is necessary to use low-energy X-rays so that the packaging material of the inspected object is visible in the X-ray transmission image. However, low-energy X-rays have low penetrating power and therefore cannot inspect thick inspected objects. Conversely, when inspecting thick inspected objects using high-energy X-rays, the packaging material does not appear in the X-ray transmission image, making it impossible to inspect for jamming.

[0006] In other words, when the X-ray inspection device disclosed in the above-mentioned Patent Document 1 was used to inspect thick contents with high accuracy, it was not possible to obtain a contrast between the belt surface and the seal area, and it was therefore not possible to extract the outline area that served as the basis for calculating the seal area.

[0007] Therefore, the present invention has been made in consideration of the above problems, and aims to provide an X-ray inspection device and an X-ray inspection method that are capable of inspecting seals without reducing the inspection accuracy of contents, even when the contents are thick. [Means for solving the problem]

[0008] In order to achieve the above object, the X-ray inspection apparatus according to claim 1 of the present invention is configured to inspect an object W to be inspected, which is a rectangular content Wb in a plan view wrapped in a packaging material Wa. The conveyor belt 11 is wound around a plurality of conveyor rollers 12, 12 in a predetermined conveying direction A at a predetermined conveying speed. An X-ray inspection apparatus (1) that inspects the quality of an object to be inspected by irradiating the object with X-rays while transporting the object and detecting the X-rays that have passed through the object to obtain an X-ray image, The object to be inspected is leading edge in the transport direction a seal portion Wc at which the packaging material is sealed on the side; The X-ray detector is provided in the upstream section near the detection position of the X-rays, The sealing portion leading edge in the transport direction a packaging material detection sensor 4 for detecting the packaging material; a content region extraction means 22 for extracting a content region of the object to be inspected from the X-ray image; The aforementioned Leading edge in the transport direction to the content area Tip Distance to the outer edge of the side based on setting information including the X-ray detection position in the conveying direction, the position of the packaging material detection sensor, and the conveying speed pseudo seal width calculation means 23 for calculating the pseudo seal width H; When the pseudo seal width is below the lower limit, the contents of the object to be inspected Tip and a seal determining means 24b for determining that there is a seal defect due to a shift to the side.

[0011] Claims of the invention 2 The X-ray inspection apparatus according to claim 1 is The packaging material detection sensor 4 is characterized in that it is a color sensor.

[0012] Claims of the invention 3 The X-ray inspection method described in the document 1 is to inspect an object W, which is a rectangular content Wb in a plan view, wrapped in a packaging material Wa. The conveyor belt 11 is wound around a plurality of conveyor rollers 12, 12 in a predetermined conveying direction A at a predetermined conveying speed. An X-ray inspection method for inspecting the quality of an object to be inspected by using an X-ray image obtained by irradiating the object with X-rays while transporting the object and detecting the X-rays that have passed through the object, comprising: The object to be inspected is leading edge in the transport direction a seal portion Wc at which the packaging material is sealed on the side; In the upstream section, near the detection position of the X-ray The sealing portion leading edge in the transport direction of Packaging material detection sensor 4 a detecting step; extracting a content region of the object from the X-ray image; The aforementioned Leading edge in the transport direction to the content area Tip Distance to the outer edge of the side based on setting information including the X-ray detection position in the conveying direction, the position of the packaging material detection sensor, and the conveying speed A step of calculating a pseudo seal width; When the pseudo seal width is below the lower limit, the contents of the object to be inspected Tip and determining that there is a seal defect due to a shift to the side. [Effects of the Invention]

[0013] According to the present invention, even if an object to be inspected has thick contents wrapped in a packaging material, seal inspection can be performed without reducing the inspection accuracy of the contents. [Brief explanation of the drawings]

[0014] [Figure 1]1 is a block diagram of an X-ray inspection apparatus according to the present invention. [Figure 2] 10 is an explanatory diagram for calculating the content area of ​​an object to be inspected and the pseudo seal width on the leading edge side in the conveying direction of the object to be inspected using the X-ray inspection device according to the present invention. FIG. [Figure 3] 4 is a flowchart for performing a seal inspection using the X-ray inspection device according to the present invention. [Figure 4] 10A and 10B are explanatory diagrams illustrating the case where the pseudo seal widths at the rear and front sides of an object to be inspected in the transport width direction are calculated using the X-ray inspection device according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0016] As shown in Figure 1, the X-ray inspection device 1 is roughly configured to include a conveying unit 2, a driving means 3, a packaging material detection sensor 4, an X-ray generator 5, an X-ray detector 6, a setting input unit 7, a signal processing unit 8, and a display unit 9.It is incorporated, for example, into a part of a conveying line, and irradiates X-rays onto the object W to be inspected while conveying it, and inspects the quality of the object W (presence of foreign matter, presence of defective seals, etc.) using the X-ray image obtained by detecting the X-rays that have passed through the object W.

[0017] The object W to be inspected is a packaging material Wa encasing contents Wb including a container (tray), the contents Wb having at least one straight side, the packaging material Wa sealed on one side of the contents Wb, and a sealed portion Wc on that side. Specifically, for example, a lunch box in which contents Wb including a container (tray) are encased in a transparent packaging material Wa corresponds to this. The object W to be inspected may be a lunch box in which the contents are contained in a container (tray) as a packaged item, or it may be a thick food product without a container (tray), such as cheese, encased in packaging material as a packaged item. Furthermore, it is preferable that the contents Wb be rectangular when viewed from above.

[0018] The transport unit 2 transports the test objects W sequentially at predetermined intervals in the transport direction A, and is configured by, for example, a loop-shaped transport belt 11 wound around a plurality of transport rollers 12, and a conveyor that can transport the test objects W sequentially in the transport direction A (rightward in Fig. 1) by an upper running section 13 of the transport belt 11, supported on a housing (not shown). The transport rollers 12 are rotationally driven by a motor serving as driving means 3, and are controlled to achieve a predetermined transport speed.

[0019] The packaging material detection sensor 4 is composed of, for example, a distance sensor, a color sensor, etc., and detects the outermost edge (outer edge) of the seal portion Wc of the packaging material Wa of the inspection object W as a specific position. When a distance sensor is used as the packaging material detection sensor 4, light from a light source (LED or laser diode) is irradiated onto the inspection object W, the light reflected from the specific position on the inspection object W is received by a light receiving element, and the received reflected light is converted into distance and output. When a color sensor is used as the packaging material detection sensor 4, light from a light projecting unit is irradiated onto the inspection object W, and the light reflected from the specific position on the inspection object W is detected by the light receiving unit as the amount of received light for each of red, blue, and green.

[0020] In addition, when the packaging material detection sensor 4 detects the rear or front side of the seal portion Wc of the packaging material Wa of the object W to be inspected in the conveying width direction B (side of the object W to be inspected), an area sensor that detects a specific position of the object W to be inspected within a predetermined area or an area camera that captures an image of the specific position of the object W to be inspected in a plane is used.

[0021] The specific position of the inspection object W is not limited to the outermost edge (outer end) of the above-mentioned seal portion Wc, but may also be a color mark attached to the seal portion Wc of the packaging material Wa or a colored seal portion Wc.

[0022] The X-ray generator 5 uses a known X-ray tube to generate X-rays of a wavelength and intensity according to the tube current and tube voltage, and is capable of irradiating the object W to be inspected on the conveyor belt 11 with fan-beam-shaped X-rays that pass through the X-ray window portion of the enclosure and are perpendicular to the conveying direction A of the conveyor unit 2.

[0023] The tube current and tube voltage of the X-ray tube of the X-ray generator 5 should be adjusted according to the material and size (particularly the dimensions in the direction in which the X-rays pass) of the object W to be inspected, and for new varieties, the setting values ​​are determined or selected so that appropriate contrast can be obtained by test imaging using the object W or sample.

[0024] The X-ray detector 6 is composed of an X-ray line sensor in which detection elements, for example, a scintillator, which is a phosphor, and a photodiode or a charge-coupled device, are arranged in an array at a predetermined pitch in the transport width direction B of the transport section 2, and are configured to detect X-rays at a predetermined resolution, and is placed at a predetermined position in the transport direction A corresponding to the X-ray irradiation position from the X-ray generator 5.

[0025] The X-ray detector 6 detects X-rays emitted from the X-ray generator 5 and transmitted through the object W or sample to be inspected for each predetermined transmission area corresponding to the detection element, converts the X-rays into an electrical signal according to the amount of transmission of the X-rays, and outputs an X-ray detection signal for each transmission area.

[0026] Then, one line of X-ray image data is accumulated for each scan from the X-ray detector 6 (X-ray line sensor) consisting of multiple detection elements arranged in a line in the main scanning direction (y direction: width direction of the conveying path) perpendicular to the conveying direction A, and is stored as an X-ray image in the memory means 21 of the signal processing unit 8, which will be described later.

[0027] Here, the scanning period T (scanning speed [repetition rate]) of the X-ray detector 6 is set so that the unit dimension in the transport direction A (x direction) and the unit dimension in the main scanning direction (y direction) are approximately equal to each other in accordance with the transport speed. As a result, the distance between adjacent elements of the X-ray detector 6 (X-ray line sensor) becomes the length per pixel in the X-ray image.

[0028] As the X-ray detector 6, a photon counting type X-ray detector capable of simultaneously acquiring images of multiple energies may be used.

[0029] The setting input unit 7 is composed of multiple keys, switches, etc. that are operated by the user to input various settings and instructions related to the inspection and display of the object W. More specifically, the setting input unit 7 sets settings for acquiring X-ray image data, such as the tube current and tube voltage of the X-ray tube of the X-ray generator 5, the scan speed of the X-ray detector 6, and the conveying speed of the conveying unit 2, as well as a threshold value for extracting the contents Wb of the object W and an allowable range of the seal width that serves as a reference for determining whether a seal defect exists in the sealed portion Wc of the object W. Furthermore, the setting input unit 7 allows the setting of detection limit values ​​that serve as a reference for determining whether a foreign object is present in the object W or whether a missing item of the contents Wb is present when multiple inspections of the contents Wb of the object W are performed. These detection limit values ​​are set appropriately depending on the type of object W and the type of foreign object to be detected.

[0030] The signal processing unit 8 is configured to include a storage means 21, a content area extraction means 22, a pseudo seal width calculation means 23, and a quality determination unit 24.

[0031] The storage means 21 stores the state of the packaging material detection sensor 4 at the timing when X-ray image data is acquired from the X-ray detector 6 (X-ray line sensor) in association with the X-ray image data. This allows the level of the packaging material detection sensor 4 to correspond to the x- and y-coordinates on the X-ray image, with the conveyance direction A as the x-axis and the conveyance width direction B as the y-axis. This data association is based on the mounting position of the packaging material detection sensor 4, the X-ray detection position, and the conveyance speed, which are set in the setting input unit 7. The X-ray image data also has density levels that correspond to gray values ​​that are lighter as the amount of transmission increases.

[0032] The content area extraction means 22 uses a threshold value set in the setting input unit 7 to extract X-ray image data having a density level exceeding the threshold value from the X-ray image data stored in the memory means 21 as a content area corresponding to the content Wb of the object W to be inspected.

[0033] 2, the pseudo seal width calculation means 23 calculates the difference in x-coordinate between the coordinate at which the packaging material detection sensor 4 detects the leading edge of the packaging material Wa of the inspection item W and the coordinate at which the leading edge of the content area corresponding to the content Wb of the inspection item W extracted by the content area extraction means 22 in the conveying direction A. This difference in x-coordinate corresponds to the time from the detection timing by the packaging material detection sensor 4 to the timing at which X-ray image data is acquired by the X-ray detector 6 (X-ray line sensor), and this time is converted into a distance based on the mounting position of the packaging material detection sensor 4, the X-ray detection position, and the conveying speed, and the value is calculated as the pseudo seal width H.

[0034] In the above explanation, the specific position of the seal portion Wc of the object W to be inspected for determining the pseudo seal width H is the leading edge in the conveying direction A, but it may also be the trailing edge of the seal portion Wc of the object W to be inspected for in the conveying direction A. Furthermore, as will be explained later, the specific position of the seal portion Wc of the object W to be inspected for determining the pseudo seal width H may also be the rear or front side in the conveying width direction B (side of the object W to be inspected).

[0035] The quality determining unit 24 determines the quality of the inspection object W, and includes a content determining means 24a and a seal determining means 24b.

[0036] The content determining means 24a performs a process of determining the quality state of the content Wb of the inspection object W (for example, a process of determining whether or not there is a foreign matter or whether or not there is a missing part) based on the X-ray image of the content area.

[0037] The seal portion determination means 24b determines whether the pseudo seal width H calculated by the pseudo seal width calculation means 23 is within the allowable range of the length (number of pixels) set in the setting input unit 7, and determines that the seal is OK if the pseudo seal width H is within the allowable range, and determines that the seal is defective if the pseudo seal width H is outside the allowable range.

[0038] The display unit 9 is configured with various display devices such as a liquid crystal display, and displays and outputs the judgment results of the quality judgment unit 24. The display unit 9 also displays an X-ray inspection image of the inspection object W that is extracted for inspection and display from the X-ray image stored in the storage means 21.

[0039] Next, the operation of calculating the pseudo seal width H of the object W to be inspected and performing a seal inspection using the X-ray inspection device 1 configured as described above will be described with reference to the flowchart in Fig. 3. Here, the explanation will be given taking as an example a case where the object W to be inspected is transported in the transport direction A so that the seal portion Wc of the object W to be inspected is positioned at the front and rear of the transport unit 2 in the transport direction A, and the pseudo seal width at the leading end of the object W to be inspected in the transport direction A is calculated and a seal inspection is performed.

[0040] When the inspection object W is conveyed in the conveying direction A by the conveying unit 2, the packaging material detection sensor 4 detects a specific position of the seal portion Wc of the inspection object W (ST1). Specifically, the packaging material detection sensor 4 detects the leading edge of the seal portion Wc of the packaging material Wa of the inspection object W as the specific position of the seal portion Wc.

[0041] Next, the content region of the inspection object W is extracted by the content region extraction means 22 of the signal processing unit 8 (ST2). Specifically, the content region extraction means 22 extracts X-ray image data having a density level exceeding a threshold from the X-ray image data stored in the storage means 21 as a content region corresponding to the content Wb of the inspection object W.

[0042] Next, the pseudo seal width calculation means 23 of the signal processing unit 8 calculates the pseudo seal width of the object W to be inspected (ST3). Specifically, the pseudo seal width calculation means 23 calculates the difference in x-coordinate from the coordinate at which the packaging material detection sensor 4 detected the leading edge of the seal portion Wc of the packaging material Wa of the object W to the coordinate at which the leading edge in the conveying direction A of the content area corresponding to the content Wb of the object W to be inspected extracted by the content area extraction means 22. This x-coordinate difference corresponds to the time from the detection timing by the packaging material detection sensor 4 to the acquisition timing of X-ray image data by the X-ray detector 6, so this time is converted into a distance from the mounting position of the packaging material detection sensor 4, the X-ray detection position, and the conveying speed to calculate the pseudo seal width H.

[0043] Next, the seal portion determination means 24b of the signal processing unit 8 performs a seal portion determination of the object W to be inspected (ST4). Specifically, the seal portion determination means 24b can set the OK / NG determination criteria for the seal portion Wc of the object W to any predetermined range using upper and lower limit values, and determines whether the pseudo seal width H is within the predetermined range. That is, if the pseudo seal width H is within the predetermined range, it is determined to be OK, and if the pseudo seal width H is outside the predetermined range, it is determined to be NG. More specifically, if the pseudo seal width H is outside the predetermined range and exceeds the upper limit, the container (tray) has shifted backward and there is a seal defect on the rear side of the object W to be inspected, and if the pseudo seal width H is below the lower limit, the container (tray) has shifted forward and there is a seal defect on the front side of the object W to be inspected, and the object W is determined to be NG and sorted.

[0044] In the above-described embodiment, the pseudo seal width at the leading end of the inspection object W in the conveying direction A is calculated by the X-ray inspection device 1 as an example. However, as shown in FIG. 4(a), the pseudo seal width at the rear or front end of the inspection object W in the conveying width direction B may also be calculated by the X-ray inspection device 1.

[0045] In this case, the area sensor serving as the packaging material detection sensor 4 is placed on the entrance side of the conveying section 2 in the conveying direction A, as shown by the dotted line in Figure 4(a). The front edge of the conveyor belt 11 of the conveyor in the conveying section 2 in the conveying width direction B is set as the reference line L, and the level from the area sensor (packaging material detection sensor 4) is converted into a distance from the reference line L at the scanning interval of the X-ray line sensor (X-ray detector 6), and a value is held.

[0046] Furthermore, the storage means 21 of the X-ray inspection device 1 stores the converted value acquired by the area sensor (packaging material detection sensor 4) in association with the X-ray image data at the timing when the X-ray image data is acquired from the X-ray line sensor (X-ray detector 6). This allows the converted value acquired by the area sensor (packaging material detection sensor 4) to correspond to the x and y coordinates on the X-ray image, with the conveyance direction A as the x-axis and the conveyance width direction B as the y-axis.

[0047] Then, the pseudo seal width calculation means 23 of the X-ray inspection device 1 converts the distance from the front edge of the content area to the reference line L, calculates the difference from the converted value obtained by the area sensor (packaging material detection sensor 4) over the length (D) of the content area in the conveying direction A, and calculates the average or maximum value as the pseudo seal width H, as shown in Figure 4(b).

[0048] 1, when the inspection object W is transported by the transport unit 2, the inspection object W is not always transported straight along the transport direction A, and one side of the contents or seal portion of the inspection object may be tilted relative to the transport direction A or the transport width direction B. For this reason, tilt correction is performed as described below.

[0049] If the contents of the object W to be inspected or one side of the seal portion is tilted relative to the conveying direction A, the tilt angles of the contents Wb of the object W to be inspected and one side of the seal portion Wc of the object W to the conveying direction A (X-axis) are calculated, and the tilts of the contents Wb of the object W to be inspected and one side of the seal portion Wc of the object W are individually corrected so as to cancel out the calculated tilt angles.

[0050] In addition, if the contents of the object W to be inspected or one side of the seal portion is inclined relative to the conveying width direction B, the inclination angles of the contents Wb of the object W to be inspected and one side of the seal portion Wc relative to the conveying width direction B (Y axis) are each calculated, and the inclination of the contents Wb of the object W to be inspected and one side of the seal portion Wc are individually corrected so as to cancel out the calculated inclination angles.

[0051] As described above, according to the present embodiment, a specific position of the seal portion Wc of the inspection object W transported along the transport direction A is detected, the content area of ​​the inspection object W is extracted from the X-ray image, the distance from the specific position to the outer edge of one side of the content area is calculated as the pseudo-seal width H, and if the calculated pseudo-seal width H is outside a predetermined range, it is determined that the seal is defective. This makes it possible to inspect the seal without reducing the inspection accuracy of the contents, even for inspection objects with thick contents wrapped in packaging material.

[0052] Moreover, it is possible to simultaneously inspect the contents of a thick object and inspect the object for seal defects, which are contradictory inspections. Similarly, by adopting this embodiment to dual-energy X-rays, it is possible to simultaneously detect hard and soft foreign objects and inspect for seal defects.

[0053] Furthermore, since there is no need for measures such as correction due to the severe temperature effects that are unique to X-rays, on-site operations can be simplified.

[0054] Furthermore, if the specific position of the seal portion Wc of the inspection object W detected by the packaging material detection sensor 4 is colored, by using a color sensor as the packaging material detection sensor 4, the specific position (for example, the leading or trailing end in the conveying direction A, or the rear or front side in the conveying width direction B) can be stably detected even if the seal portion is unstable and the distance between the sensor and the seal portion changes.

[0055] Although the best mode for the X-ray inspection apparatus and X-ray inspection method according to the present invention has been described above, the present invention is not limited to the description and drawings of this mode. In other words, it goes without saying that all other modes, embodiments, and operational techniques that are made by those skilled in the art based on this mode are included in the scope of the present invention. [Explanation of symbols]

[0056] 1 X-ray inspection equipment 2. Conveyor section 3. Driving means 4 Packaging material detection sensor 5 X-ray generator 6 X-ray detector 7 Setting input section 8 Signal Processing Section 9 Display section 11 Conveyor belt 12 Conveyor roller 13 Upper section 21 Memory means 22 Content area extraction means 23 Pseudo seal width calculation method 24 Quality Judgment Department 24a Content determination means 24b Sealed portion determination means W Inspection object Wa packaging material Wb contents Wc seal part A Conveying direction B. Conveyance width direction H Pseudo seal width L reference line

Claims

1. An X-ray inspection device (1) for inspecting the quality of an object (W) to be inspected, the object (W) having a rectangular content (Wb) in a plan view wrapped in a packaging material (Wa), is irradiated with X-rays while being conveyed in a predetermined conveying direction (A) at a predetermined conveying speed through an upper running section (13) of a conveying belt (11) wound around a plurality of conveying rollers (12, 12), and the quality of the object to be inspected is inspected using an X-ray image obtained by detecting the X-rays that have passed through the object, the object to be inspected has a sealed portion (Wc) at the leading end side of the contents in the conveying direction where a packaging material is sealed, a packaging material detection sensor (4) provided in the upstream running section near the detection position of the X-rays and detecting the leading edge of the seal portion in the conveying direction; a content region extraction means (22) for extracting a content region of the object to be inspected from the X-ray image; a pseudo seal width calculation means (23) for calculating a distance from the leading edge of the conveying direction to an outer edge of the leading edge side of the content area as a pseudo seal width (H) based on setting information including an X-ray detection position in the conveying direction, a position of the packaging material detection sensor, and the conveying speed; and a seal determination means (24b) that determines that the contents have shifted toward the tip of the inspected object and that there is a seal defect when the pseudo seal width falls below a lower limit value.

2. 2. The X-ray inspection apparatus according to claim 1, wherein the packaging material detection sensor (4) is a color sensor.

3. An X-ray inspection method for inspecting the quality of an object (W) to be inspected, the object (W) having a rectangular content (Wb) in a plan view wrapped in a packaging material (Wa), by irradiating the object with X-rays while conveying the object through an upper running section (13) of a conveyor belt (11) wound around a plurality of conveyor rollers (12, 12) in a predetermined conveying direction (A) at a predetermined conveying speed, and using an X-ray image obtained by detecting the X-rays that have passed through the object, the object to be inspected has a sealed portion (Wc) at the leading end side of the contents in the conveying direction where a packaging material is sealed, a step of detecting a leading end of the seal portion in the conveying direction by a packaging material detection sensor (4) in the vicinity of an upstream side of a detection position of the X-ray in the upper traveling section; extracting a content region of the object from the X-ray image; calculating a distance from the leading edge of the conveying direction to an outer edge of the leading edge side of the content area as a pseudo seal width based on setting information including an X-ray detection position in the conveying direction, a position of the packaging material detection sensor, and the conveying speed; and determining that the contents have shifted toward the tip of the object to be inspected and that there is a seal defect when the pseudo seal width is below a lower limit value.

Images